Organic electroluminescent compounds and organic electroluminescent device comprising the same

ABSTRACT

The present disclosure relates to organic electroluminescent compounds, and a host material, an electron buffer material, an electron transport material and an organic electroluminescent device comprising the same. By using the organic electroluminescent compounds of the present disclosure, the organic electroluminescent device secures fast electron current properties by intermolecular stacking and interaction, and thus, it is possible to provide the organic electroluminescent device having low driving voltage and/or excellent luminous efficiency and/or efficient lifespan properties.

TECHNICAL FIELD

The present disclosure relates to organic electroluminescent compoundsand an organic electroluminescent device comprising the same.

BACKGROUND ART

An electroluminescent device (EL device) is a self-light-emitting devicewhich has advantages in that it provides a wider viewing angle, agreater contrast ratio, and a faster response time. The first organic ELdevice was developed by Eastman Kodak, by using small aromatic diaminemolecules and aluminum complexes as materials for forming alight-emitting layer [Appl. Phys. Lett. 51, 913, 1987].

An organic electroluminescent device (hereinafter abbreviated as anOLED) is a device changing electrical energy to light by applyingelectricity to an organic electroluminescent material, and generally hasa structure comprising an anode, a cathode, and an organic layer betweenthe anode and the cathode. The organic layer of an OLED, if necessary,may comprise a hole injection layer, a hole transport layer, a holeauxiliary layer, a light-emitting auxiliary layer, an electron blockinglayer, a light-emitting layer (which comprises host and dopantmaterials), an electron buffer layer, a hole blocking layer, an electrontransport layer, an electron injection layer, etc. The materials usedfor the organic layer may be categorized by their functions in holeinjection materials, hole transport materials, hole auxiliary materials,light-emitting auxiliary materials, electron blocking materials,light-emitting materials, electron buffer materials, hole blockingmaterials, electron transport materials, electron injection materials,etc. In the OLED, due to an application of a voltage, holes are injectedfrom the anode to the light-emitting layer, electrons are injected fromthe cathode to the light-emitting layer, and excitons of high energiesare formed by a recombination of the holes and the electrons. By thisenergy, organic luminescent compounds reach an excited state, and lightemission occurs by emitting light from energy due to returning from theexcited state of the organic luminescent compounds to a ground state.

The most important factor determining luminous efficiency in an OLED isa light-emitting material. A light-emitting material must have highquantum efficiency, and high electron and hole mobility, and the formedlight-emitting material layer must be uniform and stable. Light-emittingmaterials are categorized into blue, green, and red light-emittingmaterials dependent on the color of the light emission, and additionallyyellow or orange light-emitting materials. In addition, light-emittingmaterials can also be categorized into host and dopant materialsaccording to their functions. Recently, the development of an OLEDhaving high efficiency and long lifespan is an urgent issue. Inparticular, considering EL characteristic requirements for a middle orlarge-sized panel of OLED, light-emitting materials showing excellentcharacteristics compared to conventional ones must be urgentlydeveloped. The host material, which acts as a solvent in a solid stateand an energy transferer, is desirable to have high purity and anappropriate molecular weight capable for a vacuum deposition.Furthermore, the host material is desirable to have high glasstransition temperature and high thermal degradation temperature toachieve thermal stability, high electro-chemical stability to achieve along lifespan, ease of forming an amorphous thin film, good adhesion tomaterials of adjacent layers, and non-migration to other layers.

Also, the electron buffer layer is equipped to improve a problem oflight-emitting luminance reduction which may occur due to change ofcurrent properties in the device when the device is exposed to a hightemperature during a process of producing panels. Thus, the propertiesof compounds comprised in the electron buffer layer are important. Inaddition, the compound used in the electron buffer layer is desirable toperform a role of controlling an electron injection by the electronwithdrawing characteristics and the electron affinity LUMO (lowestunoccupied molecular orbital) energy level, and thus may perform a roleto improve the efficiency and the lifespan of the OLED.

Meanwhile, an organometallic complex having a light-emitting functionsuch as Alq₃ was conventionally used as an electron transport materialin an OLED due to excellent electron transfer capability. However, Alq₃had a problem moving to another layer, and lowering color purity whenused in a blue light-emitting device. Thus, a new electron transportmaterial without the aforementioned problem and having a high electronaffinity that can cause an OLED to have a high luminous efficiency dueto fast electron transfer properties has been desired.

U.S. Pat. No. 8,968,887 discloses a host material comprising aphenanthrene compound as a substituent, but the host material disclosedtherein must comprise a triphenylene as a backbone.

Korean Patent Application Laid-Open No. 10-2013-42901 discloses an OLEDcomprising a compound of a phenanthro(4,3-b)thiophene, aphenanthro(4,3-b)furan or a phenanthro(4,3-b)pyrrole as a backbone.

Korean Patent Application Laid-Open No. 10-2014-57439 discloses an OLEDusing a heterocyclic compound of a benzonaphtho(2,3-d)furan structure ora benzonaphtho(2,3-d)thiophene structure as a hole transport material ora host.

DISCLOSURE OF THE INVENTION Problems to be Solved

The object of the present disclosure is to provide organicelectroluminescent compounds being effective to produce an organicelectroluminescent device having low driving voltage, and/or excellentcurrent and power efficiencies, and/or significantly improved operativelifespan.

Solution to Problems

The present inventors found that the above objective can be achieved byan organic electroluminescent compound represented by the followingformula 1:

wherein

X represents O, S, or CR₁₁R₁₂;

R₁ to R₄, each independently, represent hydrogen, deuterium, a halogen,a cyano, a substituted or unsubstituted (C1-C30)alkyl, a substituted orunsubstituted (C6-C30)aryl, a substituted or unsubstituted (3- to30-membered)heteroaryl, a substituted or unsubstituted(C3-C30)cycloalkyl, a substituted or unsubstituted (C1-C30)alkoxy, asubstituted or unsubstituted tri(C1-C30)alkylsilyl, a substituted orunsubstituted di(C1-C30)alkyl(C6-C30)arylsilyl, a substituted orunsubstituted (C1-C30)alkyldi(C6-C30)arylsilyl, a substituted orunsubstituted tri(C6-C30)arylsilyl, a substituted or unsubstituted mono-or di-(C1-C30)alkylamino, a substituted or unsubstituted mono- ordi-(C6-C30)arylamino, or a substituted or unsubstituted(C1-C30)alkyl(C6-C30)arylamino; wherein, at least one of R₁ to R₄represent a substituted or unsubstituted (C6-C30)aryl, a substituted orunsubstituted (3- to 30-membered)heteroaryl, or a substituted orunsubstituted mono- or di-(C6-C30)arylamino, with the proviso that atleast one of R₁ to R₄ does not represent a triphenylenyl;

R₁₁ and R₁₂, each independently, represent a substituted orunsubstituted (C1-C30)alkyl, a substituted or unsubstituted(C6-C30)aryl, or a substituted or unsubstituted (3- to30-membered)heteroaryl; or are linked to each other to form asubstituted or unsubstituted, mono- or polycyclic, (C3-C30) alicyclic oraromatic ring, whose carbon atom(s) may be replaced with at least oneheteroatom selected from nitrogen, oxygen, and sulfur;

a and d, each independently, represent an integer of 1 to 4; b and c,each independently, represent an integer of 1 or 2; and

the heteroaryl contains at least one heteroatom selected from B, N, O,S, Si, and P.

The compound of the present disclosure can be utilized at a holetransport layer (HTL), a light-emitting layer (EML), an electron bufferlayer (compound deposited between an electron transport layer and alight-emitting layer in a deposited device), and an electron transportlayer by bonding with various substituents due to its unique fusingpositions. Among the layers, inventors of the present disclosure foundthat the compound shows excellent device performance when it is used ata light-emitting layer, an electron transport layer, an electron bufferlayer, or both an electron transport layer and an electron buffer layer.

Meanwhile, during the charge transport in an OLED, there is apossibility for unexpected degradation due to weak bonds within thecharge transport material. One solution for overcoming such degradationis to rigidify molecular framework (see Adv. Mater. 2013, 25,2114-2129). The core structure of the compound of the present disclosurehas a rigid aromatic network which does not have rotational freedom. Thepresent inventors found that this feature would result in excellentperformance in an OLED.

Effects of the Invention

By using the organic electroluminescent compound of the presentdisclosure as a host material, an electron buffer material, or anelectron transport material, the organic electroluminescent device maysecure fast electron current properties by intermolecular stacking andinteraction, and thus, it is possible to provide the organicelectroluminescent device having low driving voltage and/or excellentluminous efficiency and/or efficient lifespan properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic view representing the structure of anOLED according to an embodiment of the present disclosure.

FIG. 2 illustrates a view representing a computational modeling resultof core structure A.

EMBODIMENTS OF THE INVENTION

Hereinafter, the present disclosure will be described in detail.However, the following description is intended to explain thedisclosure, and is not meant in any way to restrict the scope of thedisclosure.

The term “an organic electroluminescent compound” in the presentdisclosure means a compound that may be used in an OLED, and may becomprised in any layers consisting of an OLED, if necessary.

The organic electroluminescent compound represented by formula 1 will bedescribed in detail as follows.

In formula 1, X represents O, S, or CR₁₁R₁₂. Herein, R₁₁ and R₁₂, eachindependently, represent a substituted or unsubstituted (C1-C30)alkyl, asubstituted or unsubstituted (C6-C30)aryl, or a substituted orunsubstituted (3- to 30-membered)heteroaryl; or are linked to each otherto form a substituted or unsubstituted, mono- or polycyclic, (C3-C30)alicyclic or aromatic ring, whose carbon atom(s) may be replaced with atleast one heteroatom selected from nitrogen, oxygen, and sulfur. R₁₁ andR₁₂, each independently, represent preferably a substituted orunsubstituted (C1-C20)alkyl, more preferably, a substituted orunsubstituted (C1-C10)alkyl, and for example, a methyl.

In formula 1, R₁ to R₄, each independently, represent hydrogen,deuterium, a halogen, a cyano, a substituted or unsubstituted(C1-C30)alkyl, a substituted or unsubstituted (C6-C30)aryl, asubstituted or unsubstituted (3- to 30-membered)heteroaryl, asubstituted or unsubstituted (C3-C30)cycloalkyl, a substituted orunsubstituted (C1-C30)alkoxy, a substituted or unsubstitutedtri(C1-C30)alkylsilyl, a substituted or unsubstituteddi(C1-C30)alkyl(C6-C30)arylsilyl, a substituted or unsubstituted(C1-C30)alkyldi(C6-C30)arylsilyl, a substituted or unsubstitutedtri(C6-C30)arylsilyl, a substituted or unsubstituted mono- ordi-(C1-C30)alkylamino, a substituted or unsubstituted mono- ordi-(C6-C30)arylamino, or a substituted or unsubstituted(C1-C30)alkyl(C6-C30)arylamino. Herein, at least one of R₁ to R₄represents a substituted or unsubstituted (C6-C30)aryl, a substituted orunsubstituted (3- to 30-membered)heteroaryl, or a substituted orunsubstituted mono- or di-(C6-C30)arylamino, with the proviso that atleast one of R₁ to R₄ does not represent a triphenylenyl. R₁ to R₄, eachindependently, represents preferably hydrogen, a substituted orunsubstituted (C6-C25)aryl, a substituted or unsubstituted (5- to25-membered)heteroaryl, or a substituted or unsubstituted mono- ordi-(C6-C25)arylamino, more preferably, hydrogen, a substituted(C6-C18)aryl, a substituted (5- to 18-membered)heteroaryl, or asubstituted or unsubstituted di-(C6-C18)arylamino, and for example,hydrogen, a substituted triazinyl, a substituted phenyl, a substitutednaphthyl, a substituted fluorenyl, a substituted carbazolyl, asubstituted phenoxazinyl, a substituted phenothiazinyl, or a substitutedor unsubstituted di(C6-C15)arylamino.

In formula 1, a and d, each independently, represent an integer of 1 to4; b and c, each independently, represent an integer of 1 or 2.Preferably, a to d, each independently, represent 1.

In formula 1, the heteroaryl contains at least one heteroatom selectedfrom B, N, O, S, Si, and P, and preferably, one heteroatom selected fromN, O, and S.

The compound represented by formula 1 may be represented by any one ofthe following formulas 2 to 4:

In formulas 2 to 4, X, R₁ to R₄, a, b and c are as defined in formula 1.

In formulas 2 to 4, L₁ to L₃, each independently, represent a singlebond, a substituted or unsubstituted (C6-C30)arylene, or a substitutedor unsubstituted (3- to 30-membered)heteroarylene; preferably, a singlebond, a substituted or unsubstituted (C6-C25)arylene, or a substitutedor unsubstituted (5- to 25-membered)heteroarylene; and more preferably,a single bond, a substituted or unsubstituted (C6-C18)arylene, or anunsubstituted (5- to 18-membered)heteroarylene. For example, L₁ may be asingle bond, an unsubstituted phenylene, an unsubstituted naphthylene,or a substituted fluorenylene; L₂ may be a single bond, or anunsubstituted phenylene; and L₃ may be an unsubstituted carbazolylene.

In formula 2, X₁ to X₃, each independently, represent N or CH; with theproviso that at least one of X₁ to X₃ represents N, and preferably atleast two of X₁ to X₃ represent N.

In formula 2, Ar₁ and Ar₂, each independently, represent a substitutedor unsubstituted (C6-C30)aryl, or a substituted or unsubstituted (3- to30-membered)heteroaryl; preferably, a substituted or unsubstituted(C6-C25)aryl, or a substituted or unsubstituted (5- to25-membered)heteroaryl; more preferably, a substituted or unsubstituted(C6-C18)aryl, or a substituted or unsubstituted (5- to18-membered)heteroaryl; and for example, a substituted or unsubstitutedphenyl, an unsubstituted biphenyl, an unsubstituted naphthyl, asubstituted fluorenyl, a substituted carbazolyl, or an unsubstituteddibenzofuranyl.

In formulas 3 and 4, W, Y and Z, each independently, represent a singlebond, O, S, NR₁₃, or CR₁₄R₁₅, preferably, a single bond, O, S, or NR₁₃.For example, W may represent NR₁₃; Y may represent a single bond; and Zmay represent a single bond, O, or S.

Herein, R₁₃ to R₁₅, each independently, represent a substituted orunsubstituted (C1-C30)alkyl, a substituted or unsubstituted(C6-C30)aryl, or a substituted or unsubstituted (3- to30-membered)heteroaryl; or R₁₄ and R₁₅ may be linked to each other toform a substituted or unsubstituted, mono- or polycyclic, (C3-C30)alicyclic or aromatic ring, whose carbon atom(s) may be replaced with atleast one heteroatom selected from nitrogen, oxygen, and sulfur. R₁₃ toR₁₅, each independently, represent preferably, a substituted orunsubstituted (C6-C18)aryl, or a substituted or unsubstituted (5- to18-membered)heteroaryl; more preferably, an unsubstituted (C6-C12)aryl;and for example, an unsubstituted phenyl.

In formulas 3 and 4, n and m, each independently, represent an integerof 0 or 1.

In formulas 2 to 4, e represents an integer of 1 to 3, and preferably,1.

In formulas 3 and 4, f, g and h, each independently represent an integerof 1 to 4, and preferably, an integer of 1 or 2.

In formulas 3 and 4, R₅ to R₇, each independently, represent hydrogen,deuterium, a halogen, a cyano, a substituted or unsubstituted(C1-C30)alkyl, a substituted or unsubstituted (C6-C30)aryl, asubstituted or unsubstituted (3- to 30-membered)heteroaryl, asubstituted or unsubstituted (C3-C30)cycloalkyl, a substituted orunsubstituted (C1-C30)alkoxy, a substituted or unsubstitutedtri(C1-C30)alkylsilyl, a substituted or unsubstituteddi(C1-C30)alkyl(C6-C30)arylsilyl, a substituted or unsubstituted(C1-C30)alkyldi(C6-C30)arylsilyl, a substituted or unsubstitutedtri(C6-C30)arylsilyl, a substituted or unsubstituted mono- ordi-(C1-C30)alkylamino, a substituted or unsubstituted mono- ordi-(C6-C30)arylamino, or a substituted or unsubstituted(C1-C30)alkyl(C6-C30)arylamino, or are linked to an adjacentsubstituent(s) to form a substituted or unsubstituted, mono- orpolycyclic, (C3-C30) alicyclic or aromatic ring, whose carbon atom(s)may be replaced with at least one heteroatom selected from nitrogen,oxygen, and sulfur. Preferably, R₅ to R₇, each independently, representhydrogen, a substituted or unsubstituted (C6-C25)aryl, or a substitutedor unsubstituted (5- to 25-membered)heteroaryl, or are linked to anadjacent substituent(s) to form a substituted, mono- or polycyclic,(C3-C25) aromatic ring. More preferably, R₅ to R₇, each independently,represent hydrogen, a substituted or unsubstituted (C6-C18)aryl, or asubstituted or unsubstituted (5- to 20-membered)heteroaryl, or arelinked to an adjacent substituent(s) to form a substituted polycyclic(C5-C18) aromatic ring. For example, R₅ to R₇, each independently,represent hydrogen, a substituted or unsubstituted phenyl, or asubstituted or unsubstituted carbazolyl, or are linked to an adjacentsubstituent(s) and the backbone to form a fluorenyl substituted with atleast one methyl.

Herein, the term “(C1-C30)alkyl” is meant to be a linear or branchedalkyl having 1 to 30 carbon atoms constituting the chain, in which thenumber of carbon atoms is preferably 1 to 20, more preferably 1 to 10,and includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,tert-butyl, etc. The term “(C3-C30)cycloalkyl” is a mono- or polycyclichydrocarbon having 3 to 30 ring backbone carbon atoms, in which thenumber of carbon atoms is preferably 3 to 20, more preferably 3 to 7,and includes cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc. Theterm “(3- to 7-membered) heterocycloalkyl” is a cycloalkyl having 3 to7, preferably 5 to 7, ring backbone atoms, including at least oneheteroatom selected from B, N, O, S, Si, and P, preferably O, S, and N,and includes tetrahydrofuran, pyrrolidine, thiolan, tetrahydropyran,etc. The term “(C6-C30)aryl(ene)” is a monocyclic or fused ring radicalderived from an aromatic hydrocarbon having 6 to 30 ring backbone carbonatoms, in which the number of carbon atoms is preferably 6 to 20, morepreferably 6 to 15, and may comprise a spiro structure. The abovearyl(ene) may include phenyl, biphenyl, terphenyl, naphthyl, binaphthyl,phenylnaphthyl, naphthylphenyl, fluorenyl, phenylfluorenyl,benzofluorenyl, dibenzofluorenyl, phenanthrenyl, phenylphenanthrenyl,anthracenyl, indenyl, triphenylenyl, pyrenyl, tetracenyl, perylenyl,chrysenyl, naphthacenyl, fluoranthenyl, spirobifluorenyl, etc. The term“(3- to 30-membered) heteroaryl(ene)” is an aryl having 3 to 30 ringbackbone atoms, including at least one, preferably 1 to 4 heteroatomsselected from the group consisting of B, N, O, S, Si, and P. The aboveheteroaryl(ene) may be a monocyclic ring, or a fused ring condensed withat least one benzene ring; may be partially saturated; may be one formedby linking at least one heteroaryl or aryl group to a heteroaryl groupvia a single bond(s); may comprise a spiro structure; and includes amonocyclic ring-type heteroaryl such as furyl, thiophenyl, pyrrolyl,imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl, isothiazolyl,isoxazolyl, oxazolyl, oxadiazolyl, triazinyl, tetrazinyl, triazolyl,tetrazolyl, furazanyl, pyridyl, pyrazinyl, pyrimidinyl, and pyridazinyl,and a fused ring-type heteroaryl such as benzofuranyl, benzothiophenyl,isobenzofuranyl, dibenzofuranyl, dibenzothiophenyl, benzimidazolyl,benzothiazolyl, benzoisothiazolyl, benzoisoxazolyl, benzoxazolyl,isoindolyl, indolyl, benzoindolyl, indazolyl, benzothiadiazolyl,quinolyl, isoquinolyl, cinnolinyl, quinazolinyl, quinoxalinyl,carbazolyl, benzocarbazolyl, dibenzocarbazolyl, phenoxazinyl,phenothiazinyl, phenanthridinyl, benzodioxolyl, and dihydroacridinyl.Furthermore, “halogen” includes F, C1, Br, and I.

Herein, “substituted” in the expression “substituted or unsubstituted”means that a hydrogen atom in a certain functional group is replacedwith another atom or another functional group, i.e. a substituent. Thesubstituents of the substituted alkyl, the substituted aryl(ene), thesubstituted heteroaryl(ene), the substituted cycloalkyl, the substitutedalkoxy, the substituted trialkylsilyl, the substituted dialkylarylsilyl,the substituted alkyldiarylsilyl, the substituted triarylsilyl, thesubstituted mono- or di-alkylamino, the substituted mono- ordi-arylamino, the substituted alkylarylamino, and the substituted mono-or polycyclic, alicyclic or aromatic ring in R₁ to R₇, R₁₁ to R₁₅, Ar₁,Ar₂, and L₁ to L₃, each independently, are at least one selected fromthe group consisting of deuterium; a halogen; a cyano; a carboxyl; anitro; a hydroxyl; a (C1-C30)alkyl; a halo(C1-C30)alkyl; a(C2-C30)alkenyl; a (C2-C30)alkynyl; a (C1-C30)alkoxy; a(C1-C30)alkylthio; a (C3-C30)cycloalkyl; a (C3-C30)cycloalkenyl; a (3-to 7-membered)heterocycloalkyl; a (C6-C30)aryloxy; a (C6-C30)arylthio; a(5- to 30-membered)heteroaryl unsubstituted or substituted with a(C1-C30)alkyl and/or a (C6-C30)aryl; a (C6-C30)aryl unsubstituted orsubstituted with a (C6-C30)aryl, a (5- to 30-membered)heteroaryl, and/ormono- or di-(C6-C30)arylamino; a tri(C1-C30)alkylsilyl; atri(C6-C30)arylsilyl; a di(C1-C30)alkyl(C6-C30)arylsilyl; a(C1-C30)alkyldi(C6-C30)arylsilyl; an amino; a mono- ordi-(C1-C30)alkylamino; a mono- or di-(C6-C30)arylamino unsubstituted orsubstituted with a (C1-C30)alkyl; a (C1-C30)alkyl(C6-C30)arylamino; a(C1-C30)alkylcarbonyl; a (C1-C30)alkoxycarbonyl; a (C6-C30)arylcarbonyl;a di(C6-C30)arylboronyl; a di(C1-C30)alkylboronyl; a(C1-C30)alkyl(C6-C30)arylboronyl; a (C6-C30)aryl(C1-C30)alkyl; and a(C1-C30)alkyl(C6-C30)aryl; preferably, are at least one selected fromthe group consisting of a (C1-C20)alkyl; a (5- to 25-membered)heteroarylunsubstituted or substituted with (C1-C20)alkyl and/or (C6-C25)aryl; a(C6-C25)aryl unsubstituted or substituted with a (C6-C30)aryl, (5- to25-membered)heteroaryl and/or di(C6-C30)arylamino; a di(C6-C25)arylaminounsubstituted or substituted with a (C1-C20)alkyl; and a(C1-C20)alkyl(C6-C25)aryl; more preferably, at least one selected fromthe group consisting of a (C1-C10)alkyl; a (6- to 25-membered)heteroarylunsubstituted or substituted with (C1-C10)alkyl and/or (C6-C25)aryl; a(C6-C20)aryl unsubstituted or substituted with a (C6-C25)aryl, (6- to25-membered)heteroaryl and/or di(C6-C18)arylamino; a di(C6-C18)arylaminounsubstituted or substituted with a (C1-C10)alkyl; and a(C1-C10)alkyl(C6-C20)aryl; and for example, may be at least one selectedfrom the group consisting of a methyl; a phenyl unsubstituted orsubstituted with a diphenylfluorenyl, a carbazolyl and/or adiphenylamino; an unsubstituted biphenyl; an unsubstituted naphthyl, afluorenyl substituted with a methyl and/or a phenyl; a carbazolylunsubstituted or substituted with a phenyl; an unsubstituteddibenzofuranyl; a triazinyl substituted with a (C6-C25)aryl and/or a (6-to 18-membered)heteroaryl; a pyrimidinyl substituted with a naphthyl;and a di(C6-C18)arylamino unsubstituted or substituted with a methyl.

The compound represented by formula 1 includes the following compounds,but is not limited thereto:

The present disclosure also discloses an organic electroluminescentcompound comprising the compound of formula 1, and an OLED comprisingthe same.

The organic electroluminescent compound may consist of the organicelectroluminescent compound of the present disclosure as a solecompound, or may be a mixture or a composition comprising the organicelectroluminescent compound of the present disclosure and furthercomprising conventional materials generally used in organicelectroluminescent materials.

The OLED of the present disclosure may comprise a first electrode, asecond electrode, and at least one organic layer between the first andsecond electrodes. The organic layer may comprise at least one organicelectroluminescent compound of formula 1.

One of the first and second electrodes may be an anode, and the othermay be a cathode. The organic layer may comprise a light-emitting layer,and may further comprise at least one layer selected from a holeinjection layer, a hole transport layer, a hole auxiliary layer, alight-emitting auxiliary layer, an electron transport layer, an electronbuffer layer, an electron injection layer, an interlayer, a holeblocking layer, and an electron blocking layer.

Herein, the hole auxiliary layer or the light-emitting auxiliary layermay be placed between the hole transport layer and the light-emittinglayer, which may control a transport rate of a hole. The hole auxiliarylayer or the light-emitting auxiliary layer may be effective to producean OLED having excellent efficiencies and/or improved lifespan.

According to one embodiment of the present disclosure, the compoundrepresented by formula 1 may be comprised in an OLED as at least one ofa host material, an electron buffer material and an electron transportmaterial.

According to one embodiment of the present disclosure, the compoundrepresented by formula 1 may be comprised in the light-emitting layer asa host material. Preferably, the light-emitting layer may comprise atleast one dopant. If necessary, another compound besides the organicelectroluminescent compound of formula 1 may be comprised as a secondhost material. Herein, the weight ratio of the first host material tothe second host material is in the range of 1:99 to 99:1. The dopingconcentration of a dopant compound to a host compound in thelight-emitting layer is preferable to be less than 20 wt %.

The second host material can use any of the known phosphorescent hosts.Preferably, the second host material may comprise the compoundrepresented by the following formula 5:

wherein

A₁ and A₂, each independently, represent a substituted or unsubstituted(C6-C30)aryl; with the proviso that a substituent for neither A₁ nor A₂is a nitrogen-containing heteroaryl;

L represents a single bond, or a substituted or unsubstituted(C6-C30)arylene; and

Y₁ to Y₁₆, each independently, represent hydrogen, deuterium, a halogen,a cyano, a substituted or unsubstituted (C1-C30)alkyl, a substituted orunsubstituted (C2-C30)alkenyl, a substituted or unsubstituted(C2-C30)alkynyl, a substituted or unsubstituted (C3-C30)cycloalkyl, asubstituted or unsubstituted (C6-C60)aryl, a substituted orunsubstituted (3- to 30-membered) heteroaryl, a substituted orunsubstituted tri(C1-C30)alkylsilyl, a substituted or unsubstitutedtri(C6-C30)arylsilyl, a substituted or unsubstituteddi(C1-C30)alkyl(C6-C30)arylsilyl, a substituted or unsubstituted(C1-C30)alkyldi(C6-C30)arylsilyl, or a substituted or unsubstitutedmono- or di-(C6-C30)arylamino; or may be linked to an adjacentsubstituent(s) to form a substituted or unsubstituted (C3-C30), mono- orpolycyclic, alicyclic or aromatic ring, whose carbon atom(s) may bereplaced with at least one heteroatom selected from nitrogen, oxygen,and sulfur.

The compound of formula 5 may be represented by any one of the followingformulas 6 to 9.

In formulas 6 to 9, A₁, A₂, L, and Y₁ to Y₁₆ are as defined in formula5.

In formulas 5 to 9, A₁ and A₂, each independently, represent preferably,a substituted or unsubstituted (C6-C20)aryl, and more preferably, a(C6-C20)aryl unsubstituted or substituted with a cyano, a halogen, a(C1-C6)alkyl, a (C6-C12)aryl or tri(C6-C12)arylsilyl. For example, A₁and A₂, each independently, may be selected from the group consisting ofa substituted or unsubstituted phenyl, a substituted or unsubstitutedbiphenyl, a substituted or unsubstituted terphenyl, a substituted orunsubstituted naphthyl, a substituted or unsubstituted fluorenyl, asubstituted or unsubstituted benzofluorenyl, a substituted orunsubstituted phenanthrenyl, a substituted or unsubstituted anthracenyl,a substituted or unsubstituted indenyl, a substituted or unsubstitutedtriphenylenyl, a substituted or unsubstituted pyrenyl, a substituted orunsubstituted tetracenyl, a substituted or unsubstituted perylenyl, asubstituted or unsubstituted chrysenyl, a substituted or unsubstitutedphenylnaphthyl, a substituted or unsubstituted naphthylphenyl, and asubstituted or unsubstituted fluoranthenyl. The substituent of thesubstituted group such as the substituted phenyl may be a cyano, ahalogen, a (C1-C6)alkyl, a (C6-C12)aryl, or a tri(C6-C12)arylsilyl.

In formulas 5 to 9, Y₁ to Y₁₆, each independently, represent preferably,hydrogen; a cyano; a substituted or unsubstituted (C1-C10)alkyl; asubstituted or unsubstituted (C6-C20)aryl; a substituted orunsubstituted (5- to 20-membered) heteroaryl; or a substituted orunsubstituted tri(C6-C12)arylsilyl; more preferably, hydrogen; a cyano;a (C1-C10)alkyl; a (C6-C20)aryl unsubstituted or substituted with acyano, a (C1-C10)alkyl or a tri(C6-C12)arylsilyl; a (5- to 20-membered)heteroaryl unsubstituted or substituted with a (C1-C10)alkyl, a(C6-C15)aryl or a tri(C6-C12)arylsilyl; or a tri(C6-C12)arylsilylunsubstituted or substituted with a (C1-C10)alkyl. For example, Y₁ toY₁₆, each independently, represent hydrogen; a cyano; a (C1-C6)alkyl; aphenyl, a biphenyl, a terphenyl, or a naphthyl, unsubstituted orsubstituted with a cyano, a (C1-C6)alkyl or a triphenylsilyl; adibenzothiophenyl or a dibenzofuranyl, unsubstituted or substituted witha (C1-C6)alkyl, a phenyl, a biphenyl, a naphthyl or a triphenylsilyl; ora triphenylsilyl unsubstituted or substituted with a (C1-C6)alkyl.

In formulas 5 to 9, L represents a single bond, or a substituted orunsubstituted (C6-C30)arylene; preferably, a single bond, or asubstituted or unsubstituted (C6-C15)arylene; more preferably, a singlebond, or a (C6-C15)arylene unsubstituted or substituted with a cyano, a(C1-C6)alkyl or a tri(C6-C12)arylsilyl; and for example, a single bond,a substituted or unsubstituted phenylene, a substituted or unsubstitutednaphthylene, or a substituted or unsubstituted biphenylene.

Specifically, L may represent a single bond, or any one of the followingformulas 10 to 22.

wherein

Xi to Xp, each independently, represent hydrogen, deuterium, a halogen,a cyano, a substituted or unsubstituted (C1-C30)alkyl, a substituted orunsubstituted (C2-C30)alkenyl, a substituted or unsubstituted(C2-C30)alkynyl, a substituted or unsubstituted (C3-C30)cycloalkyl, asubstituted or unsubstituted (C6-C60)aryl, a substituted orunsubstituted (3- to 30-membered) heteroaryl, a substituted orunsubstituted tri(C1-C30)alkylsilyl, a substituted or unsubstitutedtri(C6-C30)arylsilyl, a substituted or unsubstituteddi(C1-C30)alkyl(C6-C30)arylsilyl, a substituted or unsubstituted(C1-C30)alkyldi(C6-C30)arylsilyl, or a substituted or unsubstitutedmono- or di-(C6-C30)arylamino; or may be linked to an adjacentsubstituent(s) to form a substituted or unsubstituted (C3-C30), mono- orpolycyclic, alicyclic or aromatic ring, whose carbon atom(s) may bereplaced with at least one heteroatom selected from the group consistingof nitrogen, oxygen, and sulfur; and represents a bonding site. Xi toXp, each independently, represent preferably, hydrogen, a halogen, acyano, a (C1-C10)alkyl, a (C3-C20)cycloalkyl, a (C6-C12)aryl, a(C1-C6)alkyldi(C6-C12)arylsilyl, or a tri(C6-C12)arylsilyl; and morepreferably, hydrogen, a cyano, a (C1-C6)alkyl, or atri(C6-C12)arylsilyl.

The compound represented by formula 5 includes the following compounds,but is not limited thereto:

When using the compound of the present disclosure as a host, at leastone phosphorescent dopant may be used as a dopont. The phosphorescentdopant material used for the OLED of the present disclosure is notparticularly limited, but may be preferably selected from metallatedcomplex compounds of iridium (Ir), osmium (Os), copper (Cu), andplatinum (Pt), more preferably selected from ortho-metallated complexcompounds of iridium (Ir), osmium (Os), copper (Cu), and platinum (Pt),and even more preferably ortho-metallated iridium complex compounds.

The dopant to be comprised in the OLED of the present disclosure may beselected from the group consisting of the compounds represented by thefollowing formulas 100 to 102.

wherein L_(d) is selected from the following structures:

R₁₀₀ represents hydrogen, deuterium, a substituted or unsubstituted(C1-C30)alkyl, or a substituted or unsubstituted (C3-C30)cycloalkyl;

R₁₀₁ to R₁₀₀ and R₁₁₁ to R₁₂₃, each independently, represent hydrogen,deuterium, a halogen, a substituted or unsubstituted (C1-C30)alkyl, asubstituted or unsubstituted (C3-C30)cycloalkyl, a cyano, or asubstituted or unsubstituted (C1-C30)alkoxy; adjacent substituents ofR₁₀₆ to R₁₀₀ may be linked to each other to form a substituted orunsubstituted fused ring, e.g., a substituted or unsubstituteddibenzofuran; and adjacent substituents of R₁₂₀ to R₁₂₃ may be linked toeach other to form a substituted or unsubstituted fused ring, e.g., asubstituted or unsubstituted quinoline;

R₁₂₄ to R₁₂₇, each independently, represent hydrogen, deuterium, ahalogen, a substituted or unsubstituted (C1-C30)alkyl, or a substitutedor unsubstituted (C6-C30)aryl; and adjacent substituents of R₁₂₄ to R₁₂₇may be linked to each other to form a substituted or unsubstituted fusedring, e.g., a substituted or unsubstituted fluorene, a substituted orunsubstituted dibenzothiophene, or a substituted or unsubstituteddibenzofuran;

R₂₀₁ to R₂₁₁, each independently, represent hydrogen, deuterium, ahalogen, a substituted or unsubstituted (C1-C30)alkyl, a substituted orunsubstituted (C3-C30)cycloalkyl, or a substituted or unsubstituted(C6-C30)aryl; and adjacent substituents of R₂₀₈ to R₂₁₁ may be linked toeach other to form a substituted or unsubstituted fused ring, e.g., asubstituted or unsubstituted dibenzofuran, or a substituted orunsubstituted dibenzothiophene;

r and s, each independently, represent an integer of 1 to 3; where r ors is an integer of 2 or more, each of R₁₀₀ may be the same or different;and

t represents an integer of 1 to 3.

Specifically, the phosphorescent dopant materials include the following:

The organic electroluminescent compound of the present disclosure may beproduced by a synthetic method known to a person skilled in the art, forexample, the following reaction scheme 1:

wherein X represents O, S, or CR₁₁R₁₂; Het-La is as defined in R₄ offormula 1; R₁, R₂, R₃, R₄, a, b, c and e are as defined in formulas 1 to4; and Hal represents halogen, for example Cl or Br.

According to one embodiment of the present disclosure, the presentdisclosure provides an electron buffer material comprising the compoundrepresented by formula 1. The electron buffer material indicates amaterial to control flow properties of an electron. For example, theelectron buffer material may trap an electron, block an electron, orlower an energy barrier between an electron transport zone and alight-emitting layer. Specifically, the electron buffer material may bean electron buffer material of an OLED. The electron buffer material inan OLED may be used in the electron buffer layer, or may also besimultaneously used in other zones such as an electron transport zone ora light-emitting layer. The electron buffer material may be a mixture ora composition further comprising conventional materials generally usedin producing an OLED.

According to another embodiment of the present disclosure, the presentdisclosure provides an electron transport material comprising thecompound represented by formula 1. The electron transport materialperforms a role to increase the chance of recombining the holes andelectrons in a light-emitting layer, by transporting an electron from acathode to a light-emitting layer smoothly and blocking the mobility ofholes uncombined in a light-emitting layer, and thus the electrontransport material indicates a material having excellent electronaffinity. Specifically, the electron transport material may be anelectron transport material of an OLED. The electron transport materialin an OLED may be used in the electron transport layer, or may also besimultaneously used in other zones such as an electron injection layer,a light-emitting layer, or an electron buffer layer. The electrontransport material may be a mixture or a composition further comprisingconventional materials generally used in producing an OLED.

According to another embodiment of the present disclosure, the OLED ofthe present disclosure may comprise a first electrode, a secondelectrode opposing the first electrode, and at least one organicelectroluminescent compound represented by formula 1 between the firstand second electrodes. Also, the OLED may comprise a light-emittinglayer between the first and second electrodes; and an electron transportzone between the light-emitting layer and the second electrode, whereinthe compound represented by formula 1 may be comprised in the electrontransport zone. Further, the OLED may further comprise an electronbuffer layer between the light-emitting layer and the second electrode,wherein the compound represented by formula 1 may be comprised in theelectron buffer layer.

In an OLED comprising first and second electrodes and a light-emittinglayer, an electron buffer layer can be disposed between thelight-emitting layer and the second electrode to focus on obtaining highefficiency and long lifespan due to electron injection controlled by theLUMO energy level of the electron buffer layer.

An electron buffer layer and an electron transport zone may be disposedbetween the light-emitting layer and the second electrode, wherein theelectron buffer layer may be disposed between the light-emitting layerand the electron transport zone, or between the electron transport zoneand the second electrode.

Herein, an electron transport zone indicates a zone in which electronsare transported from the second electrode to the light-emitting layer inthe device. The electron transport zone may comprise an electrontransport compound, a reducing dopant, or the combination thereof. Theelectron transport compound may be at least one selected from the groupconsisting of oxazole-based compounds, isoxazole-based compounds,triazole-based compounds, isothiazole-based compounds, oxadiazole-basedcompounds, thiadiazole-based compounds, perylene-based compounds, andanthracene-based compounds, aluminum complexes, and gallium complexes.The reductive dopant may be at least one selected from the groupconsisting of alkali metals, alkali metal compounds, alkaline-earthmetals, rare-earth metals, halides thereof, oxides thereof, andcomplexes thereof. In addition, the electron transport zone may comprisean electron transport layer, an electron injection layer, or both ofthem. Each of the electron transport layer and the electron injectionlayer may be comprised of two or more layers.

FIG. 1 illustrates a schematic section view of an OLED according to oneembodiment of the present disclosure. Hereinafter, the structure andpreparation method of an OLED will be explained with reference to FIG.1.

Referring to FIG. 1, an OLED 100 comprises a substrate 101, a firstelectrode 110 formed on the substrate 101, an organic layer 120 formedon the first electrode 110, and a second electrode 130 opposing thefirst electrode 110 and formed on the organic layer 120.

The organic layer 120 comprises a hole injection layer 122, a holetransport layer 123 formed on the hole injection layer 122, alight-emitting layer 125 formed on the hole transport layer 123, anelectron buffer layer 126 formed on the light-emitting layer 125, and anelectron transport zone 129 formed on the electron buffer layer 126,wherein the electron transport zone 129 comprises an electron transportlayer 127 formed on the electron buffer layer 126 and the electroninjection layer 128 formed on the electron transport layer 127.

The substrate 101 may be a glass substrate, a plastic substrate, or ametal substrate generally used in an OLED.

The first electrode 110 may be an anode, and may be formed by a materialhaving high work function. An example of the material for the firstelectrode 110 may be indium tin oxide (ITO), tin oxide (TO), indium zincoxide (IZO), indium tin zinc oxide (ITZO), or the mixture thereof. Thefirst electrode 110 may be formed by various known methods such as adeposition method, a sputtering method, etc.

FIG. 2 illustrates a computational modeling result of core structure Aof the present disclosure.

By disposing the electron buffer layer in the OLED, injection andtransport of electrons can be controlled due to the difference ofaffinities between the light-emitting layer and the electron transportzone in accordance with LUMO energy levels.

The thickness of the electron buffer layer 126 may be 1 nm or more, butis not particularly limited thereto. Specifically, the thickness of theelectron buffer layer 126 may be from 2 to 100 nm. The electron bufferlayer 126 may be formed on the light-emitting layer 125 by various knownmethods such as a vacuum vapor deposition method, a wet film-formingmethod, a laser induced thermal imaging method, etc.

When the compound of the present disclosure is used as an electrontransport material or an electron buffer material, a light-emittinglayer comprised in an OLED may comprise a host and a dopant. The hostcompound may be a phosphorescent host compound or a fluorescent hostcompound. The dopant compound may be a phosphorescent dopant compound ora fluorescent dopant compound.

A fluorescent host material may be an anthracene derivative, an aluminumcomplex, a rubrene derivative, an arylamine derivative, etc., andpreferably, an anthracene derivative.

Specifically, the fluorescent host material of the present disclosuremay include the following compounds, but is not limited thereto:

A fluorescent dopant material may be a pyrene-based derivative, anaminofluorene-based derivative, an aminoanthracene-based derivative, anaminochrysene-based derivative, etc., and preferably, a pyrene-basedderivative.

Specifically, the fluorescent dopant material of the present disclosuremay include the following compounds, but is not limited thereto:

When the light-emitting layer 125 comprise a host and a dopant, thedopant may be doped in an amount of less than about 25 wt %, preferably,less than 17 wt %, based on the total amount of the host and dopant ofthe light-emitting layer. The thickness of the light-emitting layer 125may be from about 5 nm to about 100 nm, preferably, from about 10 nm toabout 60 nm. The light-emitting layer 125 is a layer in which lightemission occurs, and may be a single layer or multiple layers of two ormore layers. When the light-emitting layer 125 is multiple layers of twoor more layers, each light-emitting layer may emit different colors oflight. For example, a white light-emitting device may be produced byforming three light-emitting layers 125, which emit the light with blue,red and green, respectively. The light-emitting layer 125 may be formedon the hole transport layer 123 by various known methods such as avacuum vapor deposition method, a wet film-forming method, a laserinduced thermal imaging method, etc.

The OLED of the present disclosure may further comprise a hole injectionlayer or a hole transport layer between the first electrode and thelight-emitting layer.

The material used in the hole injection layer 122 may be the known holeinjection material, for example, a phthalocyanine compound such as acopper phthalocyanine, MTDATA(4,4′,4″-tris[(3-methylphenyhphenylamino]triphenylamine), 2-TNATA(4,4′,4″-tris[2-naphthyl(phenyl)amino]triphenylamine),N¹,N^(1′)-([1,1′-biphenyl]-4,4′-diyl)bis(N¹-(naphthalene-1-yl)-N⁴,N⁴-diphenylbenzene-1,4-diamine),Pani/DBSA (polyaniline/dodecylbenzenesulfonic acid), PEDOT/PSS(poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate)), Pani/CSA(polyaniline/camphorsulfonic acid), or Pani/PSS(polyaniline)/poly(4-styrenesulfonate)), etc., but is not limitedthereto.

In addition, the hole injection layer 122 may be formed by using thefollowing compound of formula 200:

Wherein, R may be selected from the group consisting of a cyano (—CN), anitro (—NO₂), a phenylsulfonyl (—SO₂(C₆H₅)), a (C2-C5)alkenylsubstituted with cyano or nitro, and a phenyl substituted with a cyanoor a nitro.

The compound of the formula 200 has properties of being crystallized,and thus the hole injection layer 122 may obtain strength by comprisingthe compound.

The hole injection layer 122 may be a single layer or multiple layers oftwo or more layers. When the hole injection layer 122 is multiple layersof two or more layers, the compound of the formula 200 may be used atone of them. The thickness of the hole injection layer 122 may be fromabout 1 nm to about 1,000 nm, preferably, about 5 nm to about 100 nm.The hole injection layer 122 may be formed on the first electrode 110 byvarious known methods such as a vacuum vapor deposition method, a wetfilm-forming method, a laser induced thermal imaging method, etc.

Specifically, a hole injection material comprised in the hole injectionlayer includes the following compounds, but is not limited thereto:

The material used in the hole transport layer 123 may be the known holetransport material, for example, an aromatic amine-based derivative,especially, a biphenyldiamine-based derivative such as TPD(N,N′-bis-(3-methylphenyl)-N,N′-diphenylbenzidine),N⁴,N⁴,N^(4′),N^(4′)-tetra([1,1′-biphenyl]-4-yl)-[1,1′-biphenyl]-4,4′-diamine,etc., but is not limited thereto.

Specifically, a hole transport material comprised in the hole transportlayer includes the following compounds, but is not limited thereto:

The hole transport layer 123 may be a single layer or multiple layers.The thickness of the hole transport layer 123 may be from about 1 nm toabout 100 nm, preferably, from about 5 nm to about 80 nm. The holetransport layer 123 may be formed on the hole injection layer 122 byvarious known methods such as a vacuum vapor deposition method, a wetfilm-forming method, a laser induced thermal imaging method, etc.

When a material having improved HOMO characteristics and anion stabilityis used as a hole transport material, the lifespan properties of thedevice is also improved as the hole transport layer stabilized, even forOLEDs comprising an electron buffer layer of which lifespan isrelatively short. In other words, upon comparing using a material havingimproved HOMO characteristics and anion stability with using a materialhaving vulnerable HOMO characteristics and anion stability as a holetransport material of the hole transport layer, lifespan properties canbe prevented from being decreased by using a material having improvedHOMO characteristics and anion stability even for a device comprising anelectron buffer layer of which lifespan is relatively short, due torelatively low deviation of lifespan according to the material groupsconsisting of the electron buffer layer.

The electron transport layer 127 may comprise the known electrontransport material besides the compound of the present disclosure. Forexample, the electron transport material may be oxazole-based compounds,isoxazole-based compounds, triazole-based compounds, isothiazole-basedcompounds, oxadiazole-based compounds, thiadiazole-based compounds,perylene-based compounds, and anthracene-based compounds, aluminumcomplexes, gallium complexes, etc., but is not limited thereto.

Specifically, an electron transport material comprised in the electrontransport layer includes the following compounds, but is not limitedthereto:

Preferably, the electron transport layer 127 may be a mixed layercomprising an electron transport compound and a reductive dopant. Whenformed as a mixed layer, electrons can be easily injected andtransported to a light-emitting medium since the electron transportcompound is reduced to an anion.

When the electron transport layer 127 is formed as a mixed layer, theelectron transport compound is not specifically limited, and the knownelectron transport material may be used.

The reductive dopant may be alkali metals, alkali metal compounds,alkaline-earth metals, rare-earth metals, halides thereof, oxidesthereof, and complexes thereof. Specifically, the reductive dopantincludes lithium quinolate, sodium quinolate, cesium quinolate,potassium quinolate, LiF, NaCl, CsF, Li₂O, BaO, and BaF₂, but is notlimited thereto.

The thickness of the electron transport layer 127 may be from about 5 nmto about 100 nm, and preferably from about 10 nm to about 60 nm. Theelectron transport layer 127 may be formed on the electron buffer layer126 by various known methods such as a vacuum vapor deposition method, awet film-forming method, a laser induced thermal imaging method, etc.

The material used in the electron injection layer 128 may be the knownelectron injection materials, for example, lithium quinolate, sodiumquinolate, cesium quinolate, potassium quinolate, LiF, NaCl, CsF, Li₂O,BaO, BaF₂, etc., but are not limited thereto.

The thickness of the electron injection layer 128 may be from about 0.1nm to about 10 nm, and preferably from about 0.3 nm to about 9 nm. Theelectron injection layer 128 may be formed on the electron transportlayer 127 by various known methods such as a vacuum vapor depositionmethod, a wet film-forming method, a laser induced thermal imagingmethod, etc.

The electron injection material comprised in the electron injectionlayer may be a lithium quinoline complex metal, and specifically,includes the following compound, but is not limited thereto:

The second electrode 130 may be a cathode, and may be formed by amaterial having low work function. The material for the second electrode130 may be aluminum (Al), calcium (Ca), magnesium (Mg), silver (Ag),cesium (Cs), lithium (Li), or a combination thereof. The secondelectrode 130 may be formed by various known methods such as adeposition method, a sputtering method, etc.

The OLED of FIG. 1 is only one embodiment to be explained clearly, andthe present invention should not be limited to the embodiment but may bevaried to another mode. For example, an optional component of the OLEDof FIG. 1 besides a light-emitting layer and an electron buffer layer,such as the hole injection layer may be omitted. In addition, anoptional component may be further added. Examples of the further addedoptional component are impurity layers such as n-doping layer andp-doping layer. Moreover, the OLED may emit light from both sides byplacing a light-emitting layer each in both sides in between theimpurity layers. The light-emitting layers of both sides may emitdifferent colors. In addition, the first electrode may be a transparentelectrode and the second electrode may be a reflective electrode so thatthe OLED may be a bottom emission type, and the first electrode may be areflective electrode and the second electrode may be a transparentelectrode so that the OLED may be a top emission type. Also, a cathode,an electron transport layer, a light-emitting layer, a hole transportlayer, a hole injection layer, and an anode may be sequentiallydeposited on a substrate to be an inverted OLED.

LUMO (lowest unoccupied molecular orbital) energy level and HOMO(highest occupied molecular orbital) energy level have inherentlynegative numbers, but the LUMO energy level and the HOMO energy level inthe present disclosure are conveniently expressed as their absolutevalues. Furthermore, the comparison between LUMO energy levels is basedon their absolute values.

The LUMO energy levels of the present disclosure may be easily measuredby the various known methods. Generally, LUMO energy levels are measuredby cyclic voltammetry or ultraviolet photoelectron spectroscopy (UPS).Thus, a person skilled in the art may easily comprehend the electronbuffer layer, host material, and electron transport zone that satisfythe equational relationship of the LUMO energy levels of the presentdisclosure to practice the present disclosure. HOMO energy levels may beeasily measured by the same as the method of measuring LUMO energylevels.

Values measured by density functional theory (DFT) are used for the LUMOenergy level of the electron buffer layer. The results according to therelationship of the LUMO energy level of the electron buffer layer (Ab)and the LUMO energy level of the host (Ah) are to explain the generaltendency of the device in accordance with the overall LUMO energy groupsof the electron buffer layer, and thus results other than the above mayappear according to the inherent properties of the specific derivativesand the stability of the materials.

The electron buffer layer may be comprised in an OLED emitting everycolor including blue, red, and green, preferably, a blue light-emittingOLED (i.e. the main peak wavelength is from 430 to 470 nm, preferably,in the 450's nm).

Hereinafter, the preparation method of the compounds of the presentdisclosure, and the properties of the device comprising the compoundswill be explained in detail with reference to the representativecompounds of the present disclosure. However, the present invention isnot limited by the following examples.

Example 1: Preparation of Compound C-1

1) Preparation of Compound 1-1

After introducing 1-bromodibenzothiophene (CAS: 65642-94-6, 19.4 g, 73.7mmol), 4-chloro-2-formylbenzene boronic acid (15 g, 81.7 mmol),tetrakis(triphenylphosphine)palladium (3.4 g, 3.0 mmol), sodiumcarbonate (19.5 g, 184 mmol), toluene (400 mL), ethanol (100 mL), anddistilled water (100 mL) into a reaction vessel, the mixture was stirredfor 3 hours at 140° C. After completing the reaction by adding distilledwater to the reaction solution, an organic layer was extracted withethyl acetate. The extracted organic layer was dried with magnesiumsulfate, and the solvent was removed therefrom using a rotaryevaporator. After dissolving the product into chloroform, the productwas filtered with silica gel to obtain compound 1-1. The obtainedcompound 1-1 was used in the next reaction without any furtherpurification.

2) Preparation of Compound 1-2

After introducing compound 1-1 (24 g, 74 mmol),(methoxymethyl)triphenylphosphonium chloride (38 g, 111 mmol) andtetrahydrofuran (500 mL) into a reaction vessel, the mixture was stirredfor 5 hours. Potassium tert-butoxide (1M in THF, 111 mL) was then slowlyadded dropwise to the mixture at 0° C. The temperature of the mixturewas slowly raised, and the mixture was stirred at room temperature for 3hours. After completing the reaction by adding distilled water to thereaction solution, an organic layer was extracted with ethyl acetate.The extracted organic layer was dried with magnesium sulfate, and thesolvent was removed therefrom using a rotary evaporator. Afterdissolving the product into chloroform, the product was filtered withsilica gel to obtain compound 1-2. The obtained compound 1-2 was used inthe next reaction without any further purification.

3) Preparation of Compound 1-3

After introducing compound 1-2 (26 g, 74 mmol), Eaton's reagent (4 mL)and chlorobenzene (400 mL) into a reaction vessel, the mixture wasrefluxed for 2 hours. After completing the reaction, the mixture wascooled to room temperature, and an organic layer was extracted withmethylene chloride (MC). After drying the extracted organic layer withmagnesium sulfate, the solvent was removed by using a rotary evaporator.Thereafter, the obtained product was purified by column chromatographyto obtain compound 1-3 (16.3 g, 66%).

4) Preparation of Compound 1-4

After introducing compound 1-3 (10.5 g, 33 mmol),bis(pinacolato)diborane (10 g, 39.6 mmol),tris(dibenzylideneacetone)dipalladium (1.3 g, 1.65 mmol),2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (s-phos) (1.4 g, 3.3mmol), potassium acetate (9.7 g, 99 mmol) and 1,4-dioxane (150 mL) intoa reaction vessel, the mixture was stirred for 3 hours at 140° C. Aftercompleting the reaction, the mixture was cooled to room temperature, andan organic layer was extracted with ethyl acetate. After drying theextracted organic layer with magnesium sulfate, the solvent was removedby using a rotary evaporator. Thereafter, the obtained product waspurified by column chromatography to obtain compound 1-4 (14.3 g, 99%).

5) Preparation of Compound C-1

After introducing compound 1-4 (7.2 g, 17.6 mmol),2-chloro-4,6-diphenyl-1,3,5-triazine (CAS: 3842-55-5, 4.7 g, 17.6 mmol),tetrakis(triphenylphosphine)palladium (1.0 g, 0.88 mmol), potassiumcarbonate (6 g, 44 mmol), toluene (60 mL), ethanol (20 mL), anddistilled water (20 mL) into a reaction vessel, the mixture was stirredfor 3 hours at 140° C. After completing the reaction, the mixture wasadded dropwise to methanol, and the obtained solid was filtered. Theobtained solid was purified by column chromatography andrecrystallization to obtain compound C-1 (7 g, 77%).

Example 2: Preparation of Compound C-21

After introducing compound 1-4 (6.0 g, 14.6 mmol),2-(4-bromophenyl)-4,6-diphenyl-1,3,5-triazine (CAS: 23449-08-3, 5.2 g,13.3 mmol), tetrakis(triphenylphosphine)palladium (0.77 g, 0.67 mmol),potassium carbonate (4.6 g, 36.5 mmol), toluene (60 mL), ethanol (20mL), and distilled water (20 mL) into a reaction vessel, the mixture wasstirred for 3 hours at 140° C. After completing the reaction, theprecipitated solid was washed with distilled water and methanol. Theobtained compound was purified by column chromatography andrecrystallization to obtain compound C-21 (4.4 g, 56%).

Example 3: Preparation of Compound C-31

After introducing compound 1-3 (4 g, 12.5 mmol),9-phenyl-9H,9′H-[3,3]bicarbazolyl (CAS: 1060735-14-9, 5.1 g, 23 mmol),tris(dibenzylideneacetone)dipalladium (0.46 g, 0.50 mmol),2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (s-phos) (0.41 g, 1.00mmol), sodium tert-butoxide (2.4 g, 25.1 mmol) and o-xylene (70 mL) intoa reaction vessel, the mixture was stirred for 3 hours at 170° C. Aftercompleting the reaction, the mixture was added dropwise to methanol, andthe obtained solid was filtered. The obtained solid was purified bycolumn chromatography and recrystallization to obtain compound C-31 (6.9g, 80%).

Example 4: Preparation of Compound C-42

After introducing compound 1-4 (7.2 g, 17.6 mmol),2-(3-bromophenyl)-4,6-diphenyl-1,3,5-triazine (CAS: 864377-31-1, 4.7 g,17.6 mmol), tetrakis(triphenylphosphine)palladium (1.0 g, 0.88 mmol),potassium carbonate (6.0 g, 44 mmol), toluene (60 mL), ethanol (20 mL),and distilled water (20 mL) into a reaction vessel, the mixture wasstirred for 3 hours at 140° C. After completing the reaction, theprecipitated solid was washed with distilled water and methanol. Theobtained compound was purified by column chromatography andrecrystallization to obtain compound C-42 (5.7 g, 84%).

The properties of compounds C-1, C-21, C-31 and C-42 synthesized asdescribed above are shown in Table 1 below.

TABLE 1 UV Spectrum PL Spectrum M.P. Compound MW (in toluene, nm) (intoluene, nm) (° C.) C-1 516 280 431 301 C-21 591.72 258 427 278 C-31691.0 302 406 299 C-42 592 258 399 257

Hereinafter, the luminescent properties of the OLED comprising theorganic electroluminescent compound of the present disclosure will beexplained in detail.

Comparative Example 1: Producing a Blue Light-Emitting OLED Device notComprising an Electron Buffer Layer

An OLED device was produced as follows: A transparent electrode indiumtin oxide (ITO) thin film (10 Ω/sq) on a glass substrate for an OLED(GEOMATEC CO., LTD., Japan) was subjected to an ultrasonic washing bysequentially using acetone, ethanol, and distilled water, and was thenstored in isopropanol. Next, the ITO substrate was mounted on asubstrate holder of a vacuum vapor deposition apparatus. Compound HI-1was introduced into a cell of the vacuum vapor deposition apparatus, andthe pressure in the chamber of the apparatus was then controlled to 10⁻⁷torr. Thereafter, an electric current was applied to the cell toevaporate the introduced material, thereby forming the first holeinjection layer having a thickness of 60 nm on the ITO substrate.Compound HI-2 was then introduced into another cell of the vacuum vapordeposition apparatus, and an electric current was applied to the cell toevaporate the introduced material, thereby forming the second holeinjection layer having a thickness of 5 nm on the first hole injectionlayer. Compound HT-1 was introduced into another cell of the vacuumvapor deposition apparatus. Thereafter, an electric current was appliedto the cell to evaporate the introduced material, thereby forming thefirst hole transport layer having a thickness of 20 nm on the secondhole injection layer. Compound HT-2 was then introduced into anothercell of the vacuum vapor deposition apparatus, and an electric currentwas applied to the cell to evaporate the introduced material, therebyforming the second hole transport layer having a thickness of 5 nm onthe first hole transport layer. After forming the hole injection layersand the hole transport layers, a light-emitting layer was then depositedas follows. Compound BH-1 as a host was introduced into one cell of thevacuum vapor deposition apparatus and compound BD-1 as a dopant wasintroduced into another cell of the apparatus. The two materials wereevaporated at a different rate and the dopant was deposited in a dopingamount of 2 wt %, based on the total weight of the host and dopant, toform a light-emitting layer having a thickness of 20 nm on the secondhole transport layer. Next, compound ETL-1 as an electron transportmaterial was introduced into one cell of the vacuum vapor depositionapparatus, and compound EIL-1 was introduced into another cell of thevacuum vapor deposition apparatus. The two materials were evaporated atthe same rate and doped in a doping amount of 50 wt %, respectively, toform an electron transport layer having a thickness of 35 nm on thelight-emitting layer. After depositing compound EIL-1 having a thicknessof 2 nm as an electron injection layer on the electron transport layer,an Al cathode having a thickness of 80 nm was then deposited by anothervacuum vapor deposition apparatus on the electron injection layer. Thus,an OLED device was produced. All the materials used for producing theOLED device were purified by vacuum sublimation at 10⁻⁶ torr.

The driving voltage at the luminance of 1,000 nits, the luminousefficiency, the CIE color coordinate, the External Quantum Efficiency,and the time taken to be reduced to 90% of the luminance, where theearly luminance is 100%, at 2,000 nits and a constant current (T90lifespan) of the OLED device produced as described above are provided inTable 2 below.

Device Example 1: Producing a Blue Light-Emitting OLED Device Comprisingthe Compound of the Present Disclosure as an Electron Buffer Material

An OLED device was produced in the same manner as in Comparative Example1, that except the thickness of an electron transport layer was reducedto 25 nm, and an electron buffer layer having a thickness of 5 nm wasinserted between the light-emitting layer and the electron transportlayer. Evaluation results of the OLED device produced in Device Example1 are provided in Table 2 below.

TABLE 2 External Electron Driving Luminous Color Color Quantum LifespanBuffer Voltage Efficiency Coordinate Coordinate Efficiency T90 Material(V) (cd/A) (x) (y) (%) (hr) Comparative — 4.3 6.0 139 88 8.7 40.3Example 1 Device C-42 4.2 6.4 139 87 9.4 44.2 Example 1

From Table 2 above, it can be seen that the electron buffer material ofthe present disclosure has fast electron current properties, and thusDevice Example 1 provides high efficiency and long lifespan compared toComparative Example 1 which does not have an electron buffer material.

Comparative Example 2: Producing a Blue Light-Emitting OLED DeviceComprising a Conventional Electron Transport Material

An OLED device was produced in the same manner as in Comparative Example1, except for changing the electron transport layer and the electroninjection layer as follows: Compound ETL-2 as an electron transportmaterial was introduced into one cell of the vacuum vapor depositionapparatus and was then evaporated to form an electron transport layerhaving a thickness of 33 nm. After depositing compound EIL-1 having athickness of 4 nm as an electron injection layer, an Al cathode having athickness of 80 nm was then deposited by another vacuum vapor depositionapparatus. Thus, an OLED device was produced. Each of the materials usedfor producing the OLED device was purified by vacuum sublimation at 10⁻⁶torr.

The driving voltage at the luminance of 1,000 nits, the luminousefficiency, the CIE color coordinate, and the External QuantumEfficiency of the OLED device produced as described above are providedin Table 3 below.

Device Example 2: Producing a Blue Light-Emitting OLED Device Comprisingthe Compound of the Present Disclosure as an Electron Transport Material

An OLED device was produced in the same manner as in Comparative Example2, except for changing the electron transport material as shown in Table3 below. Evaluation results of the OLED device produced in DeviceExample 2 are provided in Table 3 below.

TABLE 3 External Electron Driving Luminous Color Color Quantum TransportVoltage Efficiency Coordinate Coordinate Efficiency Material (V) (cd/A)(x) (y) (%) Comparative ETL-2 4.6 4.6 144 115 4.8 Example 2 Device C-423.9 6.4 139 88 8.0 Example 2

Comparative Example 3: Producing a Blue Light-Emitting OLED DeviceComprising a Conventional Electron Transport Material

An OLED device was produced in the same manner as in Comparative Example2, except for changing the electron transport layer and the electroninjection layer as follows: Compound ETL-2 as an electron transportmaterial was introduced into one cell of the apparatus and compoundEIL-1 as an electron transport material was introduced into another cellof the apparatus. The two materials were evaporated at the same rate anddoped in a doping amount of 50 wt %, respectively, to deposit anelectron transport layer having a thickness of 35 nm. Next, compoundEIL-1 was deposited in the electron injection layer having a thicknessof 2 nm.

The driving voltage at the luminance of 1,000 nits, the luminousefficiency, the CIE color coordinate, and the External QuantumEfficiency of the OLED device produced as described above are providedin Table 4 below.

Device Example 3: Producing a Blue Light-Emitting OLED Device Comprisingthe Compound of the Present Disclosure as an Electron Transport Material

An OLED device was produced in the same manner as in Comparative Example3, except for changing the electron transport material as shown in Table4 below. Evaluation results of the OLED device produced in DeviceExample 3 are provided in Table 4 below.

TABLE 4 External Electron Driving Luminous Color Color Quantum TransportVoltage Efficiency Coordinate Coordinate Efficiency Material (V) (cd/A)(x) (y) (%) Comparative ETL-2:EIL-1 4.2 5.5 140 92 7.6 Example 3 DeviceC-42 4.3 6.5 139 85 9.6 Example 3

From Tables 3 and 4 above, it can be seen that the electron transportmaterial of the present disclosure has fast electron current property,and thus Device Examples 2 and 3 provide high efficiency compared toComparative Examples 2 and 3.

Device Example 4: Producing a Blue Light-Emitting OLED Device Comprisingthe Compound of the Present Disclosure as an Electron Transport Materialand not Comprising an Electron Buffer Layer

An OLED device was produced in the same manner as in Comparative Example1, except for changing the electron transport material to compound C-42.

The driving voltage at the luminance of 1,000 nits, the luminousefficiency, the CIE color coordinate, the External Quantum Efficiency,and the time taken to be reduced to 90% of the luminance, where theearly luminance is 100%, at 2,000 nits and a constant current (T90lifespan) of the OLED device produced as described above are provided inTable 5 below.

Device Examples 5 to 7: Producing a Blue Light-Emitting OLED DeviceComprising the Compound of the Present Disclosure as an ElectronTransport Material, and Further Comprising an Electron Buffer Layer

An OLED device was produced in the same manner as in Device Example 4,except that the thickness of an electron transport layer was reduced to25 nm, and an electron buffer layer having a thickness of 5 nm wasinserted between the light-emitting layer and the electron transportlayer. Evaluation results of the OLED device produced in Device Examples5 to 7 are provided in Table 5 below.

TABLE 5 External Electron Electron Driving Luminous Color Color QuantumLifespan Transport Buffer Voltage Efficiency Coordinate CoordinateEfficiency T90 Material Material (V) (cd/A) (x) (y) (%) (hr) Device C-42— 4.1 6.5 139 86 9.2 37.1 Example 4 Device C-42 BF-1 4.1 6.7 139 87 9.742.5 Example 5 Device C-42 BF-2 4.3 6.3 139 87 9.1 62.1 Example 6 DeviceC-42 C-42 4.3 6.3 139 87 9.1 49.0 Example 7

In Device Examples 5 to 7, the properties of the OLED device accordingto different electron buffer materials were evaluated by fixing compoundC-42 as an electron transport material. As shown in Table 5 above, anOLED device (Device Example 4) having excellent properties was obtainedby using the compound of the present disclosure as an electron transportmaterial, despite not comprising an electron buffer layer. Furthermore,the luminous efficiencies and the lifespan properties of the OLEDdevices (Device Examples 5 to 7), in which the compound of the presentdisclosure was used as an electron transport material and an electronbuffer material was further comprised, were improved compared to thoseof the OLED device (Device Example 4), in which the compound of thepresent disclosure was used as an electron transport material but anelectron buffer layer was not comprised. The difference of theefficiency and the performance of the OLED are due to the different HOMOorbital characteristics change of the electron buffer material used inDevice Examples 5 to 7. Specifically, it can be seen that when theelectron buffer layer comprises a diphenylfluorene and the electrontransport layer comprises a benzophenanthrothiophene as shown in DeviceExample 5, the OLED may show relatively high efficiency properties whilemaintaining a proper lifespan compared to Device Example 4. Also, it canbe seen that when the electron buffer layer comprises adiphenylindenocarbazole and a benzophenanthrothiophene, respectively,and the electron transport layer comprises a benzophenanthrothiophene asshown in Device Examples 6 and 7, the OLED may show improved lifespanproperties while maintaining proper efficiency properties compared toDevice Example 4. From Table 5 above, it can be seen that theefficiencies and lifespan properties of a OLED device may be improvednot only by using the compound of the present disclosure as an electrontransport material as a sole compound, but also by using the compound ofthe present disclosure as an electron transport material with aconventional electron buffer material or an electron buffer material ofthe present disclosure.

Device Example 8: Producing an OLED Device Comprising the ManicElectroluminescent Compounds of the Present Disclosure as a Host

An OLED device was produced as follows: A transparent electrode indiumtin oxide (ITO) thin film (10 Ω/sq) on a glass substrate for an OLEDdevice (GEOMATEC CO., LTD., Japan) was subjected to an ultrasonicwashing by sequentially using acetone, ethanol, and distilled water, andwas then stored in isopropanol. Next, the ITO substrate was mounted on asubstrate holder of a vacuum vapor deposition apparatus. Compound HI-1was introduced into a cell of the vacuum vapor deposition apparatus, andthe pressure in the chamber of the apparatus was then controlled to 10⁻⁶torr. Thereafter, an electric current was applied to the cell toevaporate the introduced material, thereby forming the first holeinjection layer having a thickness of 80 nm on the ITO substrate.Compound HI-2 was then introduced into another cell of the vacuum vapordeposition apparatus, and an electric current was applied to the cell toevaporate the introduced material, thereby forming the second holeinjection layer having a thickness of 5 nm on the first hole injectionlayer. Compound HT-1 was introduced into another cell of the vacuumvapor deposition apparatus. Thereafter, an electric current was appliedto the cell to evaporate the introduced material, thereby forming thefirst hole transport layer having a thickness of 10 nm on the secondhole injection layer. Compound HT-3 was then introduced into anothercell of the vacuum vapor deposition apparatus, and an electric currentwas applied to the cell to evaporate the introduced material, therebyforming the second hole transport layer having a thickness of 60 nm onthe first hole transport layer. After forming the hole injection layersand the hole transport layers, a light-emitting layer was then depositedas follows. Compound C-42 as a host was introduced into one cell of thevacuum vapor deposition apparatus and compound D-71 as a dopant wasintroduced into another cell of the apparatus. The two materials wereevaporated at a different rate and the dopant was deposited in a dopingamount of 3 wt %, based on the total weight of the host and dopant, toform a light-emitting layer having a thickness of 40 nm on the secondhole transport layer. Next, compound ETL-3 and compound EIL-1 were thenintroduced into another two cells, and evaporated at a rate of 1:1 toform an electron transport layer having a thickness of 30 nm on thelight-emitting layer. After depositing compound EIL-1 as an electroninjection layer having a thickness of 2 nm on the electron transportlayer, an Al cathode having a thickness of 80 nm was deposited byanother vacuum vapor deposition apparatus. Thus, an OLED device wasproduced.

As a result, the produced OLED device showed a luminous efficiency of28.2 cd/A at a driving voltage of 4.1 V, and a red light-emission havinga luminance of 1,000 nits.

Device Example 9: Producing an OLED Device Comprising OrganicElectroluminescent Compounds of the Present Disclosure as a Host and theSecond Host Compound

An OLED device was produced in the same manner as in Device Example 8,except for co-depositing compound C-42 and compound H1-12 as a host.

As a result, the produced OLED device showed a luminous efficiency of27.7 cd/A at a driving voltage 3.6 V, and a red light-emission having aluminance of 1,000 nits.

Comparative Example 4: Producing an OLED Device Comprising aConventional Compound as a Host

An OLED device was produced in the same manner as in Device Example 8,except for using compound X as a host.

As a result, the produced OLED device showed a luminous efficiency of14.3 cd/A at a driving voltage of 10 V, and a red light-emission havinga luminance of 1,000 nits.

TABLE 6 Compounds used in the Comparative Examples and Device ExamplesHole Injection Layer/ Hole Transport Layer

HI-1

HI-2

HT-1

HT-2

HT-3 Light-Emitting Layer

BH-1

BD-1 Electron Buffer layer

BF-1

BF-2 Electron Transport Layer/Electron Injection Layer

ETL-1

ETL-2

ETL-3

EIL-1

1. An organic electroluminescent compound represented by the followingformula 1:

wherein X represents O, S, or CR₁₁R₁₂; R₁ to R₄, each independently,represent hydrogen, deuterium, a halogen, a cyano, a substituted orunsubstituted (C1-C30)alkyl, a substituted or unsubstituted(C6-C30)aryl, a substituted or unsubstituted (3- to30-membered)heteroaryl, a substituted or unsubstituted(C3-C30)cycloalkyl, a substituted or unsubstituted (C1-C30)alkoxy, asubstituted or unsubstituted tri(C1-C30)alkylsilyl, a substituted orunsubstituted di(C1-C30)alkyl(C6-C30)arylsilyl, a substituted orunsubstituted (C1-C30)alkyldi(C6-C30)arylsilyl, a substituted orunsubstituted tri(C6-C30)arylsilyl, a substituted or unsubstituted mono-or di-(C1-C30)alkylamino, a substituted or unsubstituted mono- ordi-(C6-C30)arylamino, or a substituted or unsubstituted(C1-C30)alkyl(C6-C30)arylamino; wherein, at least one of R₁ to R₄represents a substituted or unsubstituted (C6-C30)aryl, a substituted orunsubstituted (3- to 30-membered)heteroaryl, or a substituted orunsubstituted mono- or di-(C6-C30)arylamino, with the proviso that atleast one of R₁ to R₄ does not represent a triphenylenyl; R₁₁ and R₁₂,each independently, represent a substituted or unsubstituted(C1-C30)alkyl, a substituted or unsubstituted (C6-C30)aryl, or asubstituted or unsubstituted (3- to 30-membered)heteroaryl; or arelinked to each other to form a substituted or unsubstituted, mono- orpolycyclic, (C3-C30) alicyclic or aromatic ring, whose carbon atom(s)may be replaced with at least one heteroatom selected from nitrogen,oxygen, and sulfur; a and d, each independently, represent an integer of1 to 4; b and c, each independently, represent an integer of 1 or 2; andthe heteroaryl contains at least one heteroatom selected from B, N, O,S, Si, and P.
 2. The organic electroluminescent compound according toclaim 1, wherein R₁ to R₄, each independently, represents hydrogen,deuterium, a substituted or unsubstituted mono- or di-(C6-C25)arylamino,a substituted or unsubstituted (C6-C25)aryl selected from phenyl,biphenyl, terphenyl, naphthyl, binaphthyl, phenylnaphthyl,naphthylphenyl, fluorenyl, phenylfluorenyl, benzofluorenyl,dibenzofluorenyl, phenanthrenyl, phenylphenanthrenyl, anthracenyl,indenyl, triphenylenyl, pyrenyl, tetracenyl, perylenyl, chrysenyl,naphthacenyl, fluoranthenyl, and spirobifluorenyl, or a substituted orunsubstituted (5- to 25-membered)heteroaryl selected from furyl,thiophenyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, thiadiazolyl,isothiazolyl, isoxazolyl, oxazolyl, oxadiazolyl, triazinyl, tetrazinyl,triazolyl, tetrazolyl, furazanyl, pyridyl, pyrazinyl, pyrimidinyl, andpyridazinyl, and a fused ring-type heteroaryl such as benzofuranyl,benzothiophenyl, isobenzofuranyl, dibenzofuranyl, dibenzothiophenyl,benzimidazolyl, benzothiazolyl, benzoisothiazolyl, benzoisoxazolyl,benzoxazolyl, isoindolyl, indolyl, benzoindolyl, indazolyl,benzothiadiazolyl, quinolyl, isoquinolyl, cinnolinyl, quinazolinyl,quinoxalinyl, carbazolyl, benzocarbazolyl, dibenzocarbazolyl,phenoxazinyl, phenothiazinyl, phenanthridinyl, benzodioxolyl, anddihydroacridinyl; X, R₁₁ to R₁₂, a, b, c and d are as defined inclaim
 1. 3. The organic electroluminescent compound according to claim1, wherein the substituents of the substituted alkyl, the substitutedaryl(ene), the substituted heteroaryl(ene), the substituted cycloalkyl,the substituted alkoxy, the substituted trialkylsilyl, the substituteddialkylarylsilyl, the substituted alkyldiarylsilyl, the substitutedtriarylsilyl, the substituted mono- or di-alkylamino, the substitutedmono- or di-arylamino, the substituted alkylarylamino, and thesubstituted mono- or polycyclic, alicyclic or aromatic ring in R₁ to R₄,R₁₁ to R₁₂, each independently, are at least one selected from the groupconsisting of deuterium; a halogen; a cyano a carboxyl; a nitro; ahydroxyl; a (C1-C30)alkyl, a halo(C1-C30)alkyl, a (C2-C30)alkenyl, a(C2-C30)alkynyl, a (C1-C30)alkoxy, a (C1-C30)alkylthio, a(C3-C30)cycloalkyl, a (C3-C30)cycloalkenyl, a (3- to7-membered)heterocycloalkyl; a (C6-C30)aryloxy, a (C6-C30)arylthio, a(5- to 30-membered)heteroaryl unsubstituted or substituted with a(C1-C30)alkyl or a (C6-C30)aryl, a (C6-C30)aryl unsubstituted orsubstituted with a (C6-C30)aryl, a (5- to 30-membered)heteroaryl, ormono- or di-(C6-C30)arylamino, a tri(C1-C30)alkylsilyl, atri(C6-C30)arylsilyl, a di(C1-C30)alkyl(C6-C30)arylsilyl, a(C1-C30)alkyldi(C6-C30)arylsilyl, an amino; a mono- ordi-(C1-C30)alkylamino, a mono- or di-(C6-C30)arylamino unsubstituted orsubstituted with a (C1-C30)alkyl, a (C1-C30)alkyl(C6-C30)arylamino, a(C1-C30)alkylcarbonyl, a (C1-C30)alkoxycarbonyl, a (C6-C30)arylcarbonyl,a di(C6-C30)arylboronyl, a di(C1-C30)alkylboronyl, a(C1-C30)alkyl(C6-C30)arylboronyl, a (C6-C30)aryl(C1-C30)alkyl, and a(C1-C30)alkyl(C6-C30)aryl.
 4. An electron buffer material comprising theorganic electroluminescent compound according to claim
 1. 5. An electrontransport material comprising the organic electroluminescent compoundaccording to claim
 1. 6. An organic electroluminescent device comprisingthe organic electroluminescent compound according to claim 1.